I've been concerned about losing the Victoria service as it is useful for those stops in between - Streatham, Balham, etc as well as the connections available at Clapham.

However, I have discovered that if I want to go to Victoria / West London, it is just as quick (if not quicker) to use the Overground in the 'wrong' direction. As an experiment last week, I went to Sloane Square from Forest Hill via Victoria and the District Line, and returned via District Line to Whitechapel and Overground to Forest Hill. Coming back was five minutes faster.